RRM2 and neoplasm: Extending these findings to an additional large independent clinical cohort of neuroblastoma patients, we performed qPCR to evaluate gene expression of CHAF1A, RRM2, MCM3 and MCM6 in tumor samples from 384 patients enrolled in the International Society of Paediatric Oncology Europe Neuroblastoma Group (SIOPEN) and the Gesellschaft fuer Paediatrische Onkologie und Haematologie (GPOH) clinical trials (validation set 6) [22].